1. Field of the Invention
The present invention relates to a drain system installed in a cutting apparatus to drain used machining water off.
2. Related Arts
Referring to FIG. 8, a cutting apparatus 70 for use in dicing semiconductor wafers comprises a chuck table 21 for holding a workpiece W thereon, and a cutting means 22 which can be driven both in the Y-axial and Z-axial directions to cut the workpiece W on the chuck table 21. The chuck table 21 is supported rotatably on a platform 24, which can be driven in the X-axial direction.
Expandable cover cloths 11 and 12 are fixed to the opposite ends of the platform 24 to cover the open top 16a of a water case 80. The cutting means 22 has a rotary blade 31 to be driven at a high-rotating speed, and machining water supply nozzles 32 placed on the opposite sides of the rotary blade 31.
A semiconductor wafer W is attached to a holder frame F via an adhesive tape T. The cutting means 22 is driven both in the Y-and Z-axial directions, while the chuck table 21 is driven in the X-axial direction reciprocatingly. Every time the cutting in the X-axial direction has been completed, the cutting means 22 is driven an incremental step in the Y-axial direction, and then, the X-axial cutting is effected. Thus, the wafer W is cut in the X-axial direction, leaving each incremental distance apart in the Y-axial direction. Then, the chuck table 21 is rotated 90 degrees, and similar cutting is repeated to dice the wafer W crosswise.
The opposite expandable cloths 11 and 12 are allowed to expand and shrink in the opposite directions when the platform 24 reciprocates in the X-axial direction. Thus, the open top 16a of the water case 80 is covered by the overlying expandable cloths 11 and 12 all the time. The machining water from the machining water supply nozzles 32 is allowed to fall in the water case 80 while being prevented from scattering by the overlying expandable cloths 11 and 12, and then, the used machining water flows in the water channels 19a, 19b, 19c and 19d, which are defined between the inner and outer surrounding walls 16 and 17, and finally, the used machining water drains off from a drain 52 without allowing it to remain and invade the inside of the cutting machine.
In a case where a workpiece of a relatively large specific gravity such as ceramic material is cutting, pulverized ceramic material is laid on the bottom of the water case 80 so that the drain channel may be clogged to allow the used machining water to overflow and invade the inside of the cutting machine.
One object of the present invention is to provide a clogging-free drain system for a cutting apparatus to prevent the used machining water from overflowing and invading the inside of the cutting apparatus even though workpieces of large specific gravity are cut.
In a cutting apparatus comprising at least a chuck table for holding a workpiece thereon, a means for driving the chuck table in the direction in which the workpiece is to be cut, and a means for cutting the workpiece on the chuck table while supplying machining water to the workpiece, a drain system is improved according to the present invention in that it comprises: an expandable cover whose opposite ends are fixed to the opposite ends of the path on which the chuck table is driven to cover the path; a water case in which the flow of the machining water is guided by the expandable cover after washing the workpiece; and a drain pool for storing the used machining water from the water case tentatively before allowing the used machining water to drain off.
The drain pool may have its bottom positioned at a level lower than the bottom of the water case, and the drain pool has its drain outlet formed at a level higher than the bottom of the drain pool. The water case may have water flow creating means for driving the used machining water to the water pool.
With the arrangement as described above, pulverized material is allowed to be deposited on the bottom of the drain pool, so that little or no pulverized material may be left on the bottom of the water case, thus preventing the used machining water from overflowing. There is no fear of the drain being clogged with pulverized material because its top opening is high above the deposition. Further, according to the water flow creating means provided in the water case, even the pulverized material of large specific gravity can be forcedly driven to the drain pool without allowing it to remain in the drain channels.
Other objects and advantages of the present invention will be understood from the following description of clogging-free drain systems according to preferred embodiments of the present invention which are shown in accompanying drawings.